Sheet-stripping apparatus



P 1968 v. c. DRAUGELIS 3,380,733

SHEET- STRIPPING APPARATUS 7 Filed Nov. 1, 1965 4 Sheets-Sheet 1 FIG.

INVENTOR. VAIDEVUTIS C. DRAUGELIS ATTORNEY April 30, 1968 V. c. DRAUGELIS SHEET-STRIPPING APPARATUS 4 Sheets-Sheet 2 Filed Nov. 1, 1965 FIG. 2

INVENTOR. 3 VAIDEVUTIS C. DRAUGELIS A TTOR/VE Y April 30, 1968 V. C. DRAUGELIS SHEET-STRIPPING APPARATUS 4 Sheets-Sheet 5 Filed Nov. 1, 1965 INVENTOR. VAIDEVUTIS c. DRAUGELIS fl/M ATTORNEY April 30, 1968 v. c. DRAUGELIS 3,330,733

SHEET-STRIPPING APPARATUS Filed Nov. 1, 1965 4 Sheets-Sheet 4 INVENTOR. VAIDEVUTIS C. DRAUGELIS A TTORNE Y United States Patent 0 3,380,733 SHEET-STRIPPING APPARATUS Vaidevutis C. Draugelis, Rochester, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Nov. 1, 1965, Ser. No. 505,905 4 Claims. (Cl. 271-51) ABSTRACT OF THE DISCLOSURE Apparatus for separating a copy sheet, supporting a toner image, from a rotating xerographic drum wherein the bond between the sheet and drum is principally electrostatic. The apparatus includes a manifold having multiple parallel spaced discharge orifices supported in a non-parallel orientation with respect to the axis of rotation of the drum. Because of this orientation, when a jet of aeriform fiuid is discharged through the manifold and orifices against the leading edge of a copy sheet rotating toward the orifices, the leading edge is stripped from the drum in a sequential manner to separate the entire sheet from the drum.

This invention relates to sheet stripping apparatus and in particular to a sheet stripping mechanism for removing sheets of transfer material from a xerographic plate.

More specifically, this invention relates to an improved sheet stripping apparatus utilizing jets of compressed aeriform fluid to strip a sheet of transfer material from a xerographic plate or similar device.

In the process of xerography, for example, as disclosed in Carlson Patent 2,297,691, a xerographic plate comprising a layer of photoconductive material on a conductive backing is given a uniform electric charge over its surface and then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate in accordance with the light intensity reaching it thereby creating an electrostatic latent image on or in the plate.

Development of the image is eifected by developers which comprise, in general, a mixture of a suitable pigmented or dyed resin based powder, hereinafter referred to as toner, and a granular carrier material which functions to carry and to generate triboelectric charges on the toner. More specifically, the function of the carrier material is to provide mechanical control of the toner, or to carry the toner to an image surface and, simultaneously, provide almost complete homogenity of charge polarity. In the development of the image, the toner powder is brought into surface contact with the photoconductive coating and is held thereon electrostatically in a pattern corresponding to the latent electrostatic image. Thereafter, the developed xerographic image is usually transferred to a transfer or support material to which it may be fixed by any suitable means.

In the mixture of toner particles in carrier material, the toner particles, which are many times smaller than the carrier particles, adhere to and coat the surface of the carrier particles due to the electrostatic attraction between them. During development, as the toner coated carrier particles roll or tumble over the xerographic plate carrying an electrostatic image of opposite polarity to the charge on the toner, toner particles are pulled away from the carrier by the latent electrostatic image and deposited on the plate to form a developed toner image.

Because of the electrostatic charges placed upon the support material, the support material electrostatically adheres to the xerographic plate. A device commonly 3,336,?33 Patented Apr. 30, 1968 used in the printing art, mechanical strip fingers, cannot be successfully used as a means for stripping the support material from a xerographic plate. Since mechanical strip fingers, in order to strip a sheet of support material from a xerographic plate, must be inserted between the support material and the plate, they will inadvertently graze and mar the photoconductive surface. Also during this process, as the support material is peeled from the xerographic plate by the strip fingers, the surface of the support material carrying the transferred images will slide on the strip fingers. The xerographic image at this time is held on the support material by electrostatic forces only, the image areas brushing against the surface of the strip fingers would, therefore, be disfigured.

In addition, since the toner image is normally negatively charged and its transfer to the support material is effected by applying a positive charge to the non-image side of the support material by means of a transfer corotron, if the charged support material contacts a grounded portion of the machine, such as mechanical strip fingers, the toner powder images will explode, losing their image configuration.

To overcome the problems involved with mechanical stripping devices, a sheet stripping apparatus, subject of I. Rutkus, Jr., et al. Patent No. 3,662,536, was developed. This invention comprises an improvement of that patent.

As the highly competitive electrostatic copying industry has progressed, it has become necessary to develop copying machines which are operative over Wide ranges of environmental conditions such as humidity, temperature and altitude, and capable of increased speed of reproduction.

Prior art sheet stripping apparatus, for example, of the type disclosed in the J. Rutkus et al. patent, required that a sheet of support material be precisely registered in relation to the discharge of compressed aeriform fiuid from the stripper mechanism to effect removal of the sheet from the xerographic drum. In automatic xerographic reproducing machines having a reproduction rate sufilciently slow to allow precise registration of the support material with the discharge of aeriform fiuid, a device such as disclosed in the above-referenced patent, is very suitable. However, as the copying speed of the xerographic machines is increased, it has been found that the support material will not register at a precise position in regard to the discharge of compressed aeriform fiuid from the sheet stripping apparatus; and, therefore, an improved sheet stripping apparatus, the subject of this invention, was developed.

The present invention comprises an improved sheet stripping apparatus having an increased latitude of operation for use in an automatic xerographic reproducing machine to strip a sheet of support material from the xerographie drum.

It is, therefore, an object of this invention to improve sheet stripping apparatus for removing electrostatically adhering transfer material from a xerographic plate without incurring harm to the photoconductive surface of the xerographic plate and without disfiguration of an electrostatically adhering xerographic image on the transfer material.

Another object of this invention is to improve sheet stripping apparatus utilizing compressed aeriform fluid to sequentially strip a portion of the support material from a xerographic drum.

These and other objects are attained in accordance with the present invention wherein there is provided a source of compressed aeriform fluid at substantially a constant pressure, connected to a discharge manifold having multiple parallel spaced orifices. The manifold is adapted to be positioned adjacent a xerographic drum at an angle to the drums axis of rotation whereby a sheet of transfer material adhering to the xerographic drum will be sequentially separated therefrom by jets of compressed aeriform fluid directed against the drum and leading edge of the sheet of support material.

Further objects of the invention, together with additional features contributing thereto and advantages accruing therefrom, will be apparent from the following description of an embodiment of the invention when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of an automatic xerographic reproducing machine utilizing an embodiment of this invention.

FIG. 2 is a horizontal elevation of the subject invention in a machine such as shown in FIG. 1 to better illustrate the cooperative relation thereof.

FIG. 3 is a side elevation view of the subject invention in a suitable environment such as the automatic xerographic reproducing machine of FIG. 1.

FIG. 4 is a front perspective view of an embodiment of the invention to more clearly illustrate the nature thereof.

FIG. 5 is a schematic diagram of the subject invention.

Referring now to FIG. 1, there is shown an embodiment of the subject invention in a suitable environment such as an automatic xerographic reproducing machine having a xerographic plate including a photoconductive layer or light-receiving surface on a conductive backing and formed in the shape of a drum, which is mounted on a shaft journaled in a frame to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally, as follows:

A charging station 1, at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

An exposure station 2, at which a light or radiation pattern of copy to be reproduced is projected onto the drum surface to dissipate the drum charge in the exposed areas thereof thereby forming a latent electrostatic image of the copy to be reproduced;

A developing station 3, at which xerographic developing material, including toner particles having an electrostatic charge opposite to that of the electrostatic latent image, are cascaded over the drum surface, whereby the toner particles adhere to the electrostatic latent image to form a xerographic powder image in the configuration of the copy being reproduced;

A transfer station 4, at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer or support material; and

A drum cleaning and discharge station 5, at which the drum surface is brushed to remove residual toner particles remaining thereon after image transfer, and at which the drum surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

It is believed that the foregoing description is sulficient for the purposes of this application to show the general operation of a Xerographic reproducing apparatus using a sheet stripper mechanism constructed in accordance with the invention. For further details concerning the specific construction of the xerographic apparatus shown, reference is made to copending application, Serial No. 400,542, now Patent No. 3,301,126, filed on September 30, 1964, in the name of Robert F. Osborne et a1.

At the image transfer station 4, the powder images previously formed on the xerographic drum are electrostatically transferred to a sheet of support material, the electrostatic charge being applied to the support material by means of the corona transfer device 7. The electrostatic charge applied to the support material during the transfer process is sufiicient to cause the support material to adhere to the drum even after the material has passed out of the corona emission area. It is apparent that there must be provided some means for removing the support material from the xerographic drum.

To prevent destruction of the powder images on the support material and to prevent damaging the drum, there is provided a sheet stripping apparatus constructed in accordance with the invention.

A preferred form of a pick-off mechanism, constructed in accordance with the invention, is specifically illustrated in FIGS. 2, 3 and 4 and employs a manifold having multiple outlet orifices 27 directed against the surface 11 of the xerographic drum so that jets of compressed aeriform fluid from the orifices are directed against the leading edge of a sheet of support material to blow the edge of the material off of the drum, the remainder of the support material then peeling off the drum due to its own weight. The manifold may be supplied with compressed aeriform fluid by means of any source of compressed aeriform fluid desirably at substantially constant pressure.

Specifically in the embodiment disclosed, there is provided a discharge manifold 25 positioned adjacent to the drum 10 and at an angle to the drums axis of rotation 12 by means of brackets 21 which may be secured to a structural element of the machine, as for example, the drum cleaning device 22. Multiple parallel spaced outlet orifices 27 secured on the manifold are positioned so that streams of compressed aeriform fluid emerging from the orifices are directed to stroke the surface of the Xerographic drum at an angle between the normal and the tangent to the drums surface.

The manifold 25 consists of tube 25 closed at one end and counterbored at the intake ends to receive the tube coupling 28 press fitted into place. Each orifice passes through the wall of tube 26 so that each is in communication with the interior thereof.

Compressed aeriform fluid is delivered to the manifold by means of a flexible tube 29 connected at one end to the manifold tube coupling 28 and its other end to the male hose connector 30 threaded into a solenoid valve 3 1 of any suitable commercial avail-able type. The solenoid valve 31 is activated whenever a sheet of support material is forwarded to the xerographic drum closing a limit switch 15. The valve is held open to allow the compressed aeriform fluid to be directed against the drum and leading edge of the support material for a suflicient time to allow the material to be sequentially removed from the drum without effecting the toner powder image electrostatically transferred to the support material, preferably 3 of the drum rotation.

Constant pressure compressed aeriform fluid is supplied to the manifold 25 through the solenoid valve 31 by means of an accumulator tank 35 and a compressor 36 as shown schematically in FIG. 5. The compressor 36 operates to keep the accumulator tank 35 at a constant suitable pressure, preferably about 13 p.s.i. by means of a pressure relief valve 37. A pressure switch 38 operates the compressor 36 whenever the accumulator tank pressure drops below a predetermined minimum and then interrupts operation when the pressure is again suitable. In the embodiment shown, when the solenoid is actuated, the valve opens for about 0.036 second, which is equivalent to 3 of drum rotation, discharging the aeriforrn fluid at substantially a constant pressure, thereafter reclosing allowing the accumulator tank to again be brought up to the original pressure.

At the transfer station 4, the toner powder image is substantially removed from the drum surface onto the support material by means of a corona transfer device 7 that is located at or immediately after the line of contact between the support material and the rotating drum. In operation, the electrostatic field created by the corona transfer device is effective to tack the support material electrostatically to the drum surface, whereby the support material moves synchronously with the drum while in contact therewith. Simultaneously with the tacking action, the electrostatic field is effective to transfer the toner particles comprising the xerographic powder image from the drum surface and cause them to adhere electrostatically to the surface of the support material.

It has been found that the registration of the support material with the discharge of compressed aeriform fluid cannot be precisely elfectuated at a predetermined point, but occur throughout a range of positions. As a result of extensive experimentation, it was determined that positioning the manifold adjacent to the xerographic drum and at an angle to the drums axis of rotation 12, prefera'bly at about a %-inch tilt in the vertical plane, will sequentially strip the support material from the xerographic drum. The discharge of compound aeriform fluid onto the xerographic drum and the leading edge of the support material strips the support material from the drum at one point proceeding across the leading edge of the drum until the entire edge is free, allowing the supporting material to drop from the drum of its own weight. The length of time of the discharge from the stripping apparatus must be of sufiicient duration to remove the support material from the drum without destroying the toner powder images electrostatically adhering thereto.

By positioning the manifold in a non parallel relation to the drums axis of rotation, a greater capability of stripping sheets from the xerographic drum can be achieved per length of pulse. For example, if the manifold were positioned parallel to the axis of rotation of the xerographic drum, as disclosed in the Rutkus et a1. patent, the latitude of stripping sheets would be determined by the length of time aeriform fluid is discharged through the manifold. A method of increasing the latitude of sheet removal by increasing the duration of the discharge of aeriform fluid has the disadvantage of destroying the toner powder image on the support material if the duration of discharge is increased beyond a very limited time. However, by positioning the manifold adjacent the xerographic drum at an angle to it axis of rotation, the range of removal of support material can be increased beyond the duration of time of discharge of compressed aeriform fluid, thereby allowing the discharge to be timed to prevent destruction of the toner powder image on the support material, but being capable of sufficient latitude to sequentially strip support material from the xerographic drum through an increased range of registration.

While the invention has been described with reference to the structure disclosed herein, it is not confined to the details set forth; and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.

What is claimed is:

1. Apparatus for the removal of sheet support material electrostatically adhering to a xerographic drum having a powder image previously formed thereon which has been substantially transferred to the support material, the powder image being maintained on the drum and the support material by electrostatic forces only, the apparatus including a source of compressed aeriform fluid,

a discharge manifold having multiple parallel paced discharge orifices operatively connected to said source,

cyclically operative means to discharge said compressed aeriform fluid through said discharge manifold,

mounting means connected to said discharge manifold to permit said manifold to be mounted adjacent to said xerographic drum in a non-parallel orientation with respect to the axis of rotation of said xerographic drum whereby jets of compressed aeriform fluid may be directed by said discharge orifices against said xerographic drum in advance of the leading edge of support mate-rial electrostatic-ally adhering to the drum to sequentially separate the leading edge of the transfer material therefrom, and

timing means connected to said cyclically operative means to limit the duration of the jets of compressed aeriform fluid from said discharge orifices so that the powder image electrostatically adhering to said xerographic drum and to said transfer material is not dislodged therefrom.

2. In a xerographic reproducing apparatus wherein an electrostatic latent image formed on a rotating xerographic drum is developed by a powder to form a visible powder image on the xerographic drum which is then transferred from the xerographic drum to support mate rial, the support material adhering electrostatically to the xerographic drum during the transfer process, the powder image being maintained on the support material by electrostatic forces, the combination of a discharge manifold having multiple discharge orifices,

mounting means connected to said discharge manifold to position said discharge manifold adjacent to said xerographic drum and at an angle to the axis of rotation of said xerographic drum,

a compressed aeriform fluid source means connected to said discharge manifold so that jets of compressed aeriform fluid may be directed by said discharge orifices against said xerographic drum to sequentially separate the leading edge of the support material from said xerographic drum, and

timing means to limit the duration of the jet streams from said orifices so that the powder adhering to the support material is not blown therefrom.

3. A sheet pick-off apparatus for the removal of support material superposed on a powder image previously formed on a xerographic drum with its leading edge extending beyond the powder image, the support material electrostatically adhering to the surface of said drum, said sheet pick-off apparatus including a manifold having multiple parallel spaced discharge orifices for the discharge of compressed aeriform fluid at substantially a constant pressure,

mounting means connected to said manifold to enable said manifold to be positioned adjacent to said drum at an angle to the drums axis of rotation with said discharge orifices of said manifold positioned to direct jets of compressed aeriform fluid against the surface of said drum in advance of the leading edge of support material thereon,

cyclically operative means to discharge said compressed aeriform fluid through said discharge manifold, and

timing means to control said cyclically operative means whereby the duration of the flow of compressed aeriform fluid from said discharge orifices is limited so that the powder image adhering electrostatically to said support material is not dislodged therefrom.

4. A sheet pick-off apparatus for the removal of support material superposed on a powder image previously formed on a rotatable cylindrical xerographic surface, the support material electrostatically adhering to the xerographic surface, said sheet pick-01f apparatus including a manifold having multiple spaced discharged orifices for the discharge of compressed aeriform fluid against the xerographic surface,

mounting means to secure the manifold with contiguous orifices being located sequentially adjacent contiguous lines on the cylindrical xerographic surface which are parallel to the axis of rotation of the cylindrical xerographic surface,

means to connect the manifold to a source of compressed aeriform fluid and means to discharge compressed aeriform fluid through said discharge manifold and said orifices so that the leading edge of a copy sheet adhering to the xero- 7 8 graphic surface will be removed therefrom in a se- 2,905,465 9/1959 Armstrong et a1. 271-74 X quential manner by the jets of aeriform fluid dis- 3,090,616 5/1963 Eichler et a1 27171 X charged through said orifices.

EDWARD A. SROKA, Primary Examiner.

References Cited 5 EVON c. BLUNK, Examiner. UNITED STATES PATENTS M. L. AJEMAN, Assistant Examiner. 2,132,132 10/1938 Seat 137-412 x 

